FYI Brex isn't a bank although they do have a business account product similar to a checking account.

To answer your question though, Brex uses AI for a lot of things some of which being:

1. Fraud/Risk/Underwriting

2. Auto-generated receipts and data enrichment

3. AI assistants for all users that have a ton of capabilities

There's a lot more as well but these are just some of the obvious ones.